二维动床泥沙数学模型在“单向冲刷”江道中的应用——以曹娥江为例

Application of the two-dimensional movable-bed mathematical model to the single-direction erosion river:a case study of Cao'e River

2008年底曹娥江河口大闸建成并开始试运行,大闸的兴建阻挡了钱塘江潮流的上朔.平时大闸关闸挡潮,阻挡外海泥沙进入上游江道;洪水期开闸放水,逐步带出建闸前淤积在河床上的泥沙.闸上江道的冲淤特性由建闸前的"洪冲枯淤"转变为建闸后的"单向冲刷",泥沙运动规律的改变将会加剧水流对两岸防洪堤的冲刷,也会对沿江涉水工程(如跨江大桥)的安全造成不同程度的影响.应用二维动床泥沙数学模型,考虑曹娥江大闸调度原则,并按水文年(1962～2005年)重演方式,对建闸后闸上江道冲淤演变情况进行了长系列反演计算,同时对堤防可能的险工险段及河床最大冲深进行了预测,可供相关部门和单位在工程设计、施工过程中参考使用.

The estuary floodgate of Cao＇e River was completed and started to trial operation to block the tide of Qian Tang River at the end of 2008. The operation of the estuary floodgate is based on a self-cleaning mechanism： the floodgate opens during the flood period so that the sediment deposited on the river bed is gradually scoured by the flood; then the flood gate closes to prevent the sediments silting-up the upstream during the other period. In this sit- uation, the erosion-deposition mode of the river upstream channel changes from ＂scouring during flood and silting during tide＂ to ＂single-direction scouring＂, whi.ch increases the erosion of the levees according to the sediment move- ment law and endangers the safety of the levees and water-related projects. In this paper, based on the dispatching principle of Cao＇e River floodgate, we used the two-dimensional movable-bed mathematical model to study the evolu- tion-deposition variation of the upstream channel followed the recurrence of hydrological year. This model can also be used to predict the maximum scour depth of the flood-bed, and further provide a scientific basis for the process control of project design and construction.